1. Field of the Invention
The invention relates to the field of turbomachines and compressors. More particularly, the invention relates to improving the pressure ratio obtainable by a turbomachine or compressor having a given blade speed and number of stages of compression and to increasing the thermodynamic efficiency of the turbomachine or compressor.
2. Prior Art
Thought about fluid dynamics and invention pertaining thereto has existed for a substantial period of time. So too has man's interest in creating power persevered. One of the arts in which substantial and powerful thought has been devoted to is that of compressors and turbomachines. One of the most important areas driving such research is aeronautics and astronautics for both the commercial interests of high speed transportation and military interests for defense and the exploration of space. Some important issues with respect to the advance of compressors and turbomachines is the pressure ratio attainable and the efficiency of the machines.
Reissue U.S. Pat. No. 23,108 to E. A. Stalker discloses the provision of slots located well rearward on the blade to increase the effectiveness of the blade. This is taught in order to control the boundary layer on the blades of blowers and compressors to better enable the machine to run at lower than optimal speeds.
J. R. Irwin, U.S. Pat. No. 2,720,356 imposes continuous boundary layer control for compressors by moving the boundary layer through porous surfaces. The teaching recommends to then reintroduce the viscous interactive flow to the main flow of the compressor at a later stage.
U.S. Pat. No. 2,749,025 to Stalker focuses primarily on providing blades of later stages in a compressor with progressively larger radii rounded leading edges. This reduces losses associated with the flow angle into these blades which would normally be experienced at below optimum speeds. The substantially semi-circular nose cross-section is professed to be able to smooth the flow and avoid burbling when the approach vectors are far from optimum. A further step to assist the machine in these conditions is to remove the boundary layer in this area.
U.S. Pat. No. 3,694,102 to Conrad teaches use of suction slots in stator blades to prevent separation of the boundary layer in supersonic blading. Conrad, however, fails to recognize the benefit of removing the boundary layer permanently from a compressor. This is evidenced by equating bleeding of the boundary layer to atmosphere to reintroducing the boundary layer into the compressor at another stage.
U.S. Pat. No. 3,993,414 to Meauze discloses an axial supersonic compressor comprising a casing and a hub rotating in the casing and carrying blades. On each of the suction surfaces of the blades is formed a zone in which the curvative changes and which corresponds to a supersonic subsonic shock wave. A channel formed in each blade and opening in the zone is connected to a boundary layer aspiration means.
U.S. Pat No. 3,897,168 to Amos and U.S. Pat No. 4,595,339 to Naudet both disclose the recapture of energy from a withdrawn boundary layer to avoid losses.
U.S. Pat No. 3,385,509 to Garnier discloses an engine with counter-rotating compressor blades and counter-rotating turbine blades. Nozzle flow area of the turbines is adjusted to control the boundary layer by either moving the stators or by blowing through slots in their surfaces. Gamier is silent however on removing the boundary layer from the flow permanently.
None of the prior art discussed provides insight to the thermodynamic benefits of fluid removal from the flow path. In fact, many of skill in the prior art believed that reintroducing the fluid of the viscous interaction to the flow path at another compressor stage was beneficial to the functioning of the machine.
It is well known in the prior art to construct compressors and turbomachines having counter-rotating blades. However, counter-rotating machines have never been as useful as they should be in view of the better compression attainable with counter-rotating blades as opposed to alternating rotating and stator blades because of mechanical factors which limited the total attainable pressure to levels not commercially viable. Unfortunately, mechanical arrangements do not exist to enable the use of more than two counter-rotating blade rows, all with high blade speeds. Prior conceptions of counter-rotating compressors have had one set of rotating blades mounted on a rotating casing, rather than a hub. This limits their blade speed. Therefore, the machines have been disappointing. Providing a means to make these machines function better would be an important advance to the industry primarily because they are less expensive to manufacture and weigh less than conventional machines.